It is known to form a cross-sectional profile of a tubular member by a hydroforming process in which a fluid filled tubular member is placed within a cavity of a die and then the die is closed so that the tubular member is pinched within the die. Fluid pressure is then increased inside the tubular member to expand the tubular member outwardly against the cavity of the die to provide a tubular member having a die formed cross-sectional profile.
During hydroforming of the tubular member, conventional hydraulic presses are used. These presses are large, expensive tools used in the hydroforming process mainly as clamping fixtures to keep a die closed against the hydroform fluid pressure. Conventional hydraulic presses require tremendous energy to keep the die halves of the die closed during the hydroforming process.
To use hydroforming to produce tubular frame rails has created a situation where even the largest hydraulic presses are not able to generate sufficient force to simultaneously hydroform both cavities in a dual cavity die. The force from the highly pressurized forming fluid works directly against the force applied by the press to keep the die closed. The difficultly in keeping the die closed is so great, that some dual cavity dies cannot hydroform both tubular members or parts simultaneously. The effect of pressurizing a single cavity in a dual cavity die not only adds tremendous stress from the off-center part, but it also doubles the part forming time.
As a result, it is desirable to provide a clamp assembly to keep a die set closed during the hydroforming process. It is also desirable to provide a clamp assembly for hydroforming that eliminates the need of larger hydraulic cylinder systems to keep a die set closed during the hydroforming process. It is further desirable to provide a clamp assembly that is less expensive than a hydraulic cylinder to keep a die set closed during the hydroforming process. Therefore, there is a need in the art to provide a new clamp assembly for a hydroforming die that meets at least one of these desires.